Apparatus for measuring the characteristic parameters of an overhead railway or traming line

ABSTRACT

An apparatus for measuring the characteristic parameters of an overhead railway or tramway line, characterized by comprising, on board a railway or tramway vehicle ( 25 ): 
     at least one laser source ( 2 ) for generating a laser beam, 
     optical means for transforming said laser beam, generated by said soruce ( 2 ), into a flat beam ( 4 ), 
     means for orientating the axis of said flat beam ( 4 ) at an angle other than 90° to the axis of the overhead line wire ( 6 ) and defining with this latter a plane substantially perpendicular to the plane of said beam ( 4 ), 
     at least one video camera ( 8 ) having its optical axis different from the axis of said flat beam but lying in said perpendicular plane and orientated towards the light-emitting line of intersection of said laser beam ( 4 ) with said wire ( 6 ), the apparatus also comprising a processing unit for the signals generated by said video camera ( 8 ) in order to determine the position of said light-emitting line within the optical field of said video camera ( 8 ), and to effect reconstruction of the real profile of said wire ( 6 ) and its comparison with the theoretical profile of the wire itself.

This invention relates to an apparatus for measuring the characteristicparameters of an overhead railway or tramway line.

BACKGROUND OF THE INVENTION

Overhead railway or tramway lines comprise one, or more often two,side-by-side electrically powered wires of convenient diameter supportedby a plurality of poles disposed along the track at a predeterminedheight therefrom, to enable a pantograph mounted on the locomotive ofthe railway or tramway train to slide along the wires and withdrawtherefrom the electrical energy required for powering the traction motorand the services.

For efficiency reasons, the overhead line has to be carefully monitoredperiodically, by measuring its characteristic parameters consistingessentially of its wear, its height and the movement of its wires.

A knowledge of the degree of wire wear is important to prevent itsdiameter falling below predetermined limiting values, which could resultin breakage of the cable subjected to continuous stress by thepantograph.

A knowledge of the wire height, i.e. its distance from the track planemeasured in a vertical direction, is important to ensure that heightvariations do not exceed a predetermined amount, typically of 1.5 m.

A knowledge of the wire movement, i.e. its distance from the track axismeasured in a horizontal direction, is important to ensure that itsvariations do not exceed a predetermined amount, typically of 0.6 m.

The parameters of an overhead railway or tramway line are currentlydetermined by a series of measurements made by a sampling guage.

Such a measurement system is evidently extremely unsatisfactory in thatit involves in particular:

extreme operational slowness because of the need to use manual sampling,

likewise extreme operational discomfort, because of the need to make amanual measurement, after firstly halting the measurement train eachtime this measurement is to be made,

only few parameters are measured,

an inevitable while at the same time unacceptable location of themeasurements at points often distant from each other and not necessarilycoinciding with the points of effective maximum wear, which are in factthose responsible for wire breakage as a result of stressing by thepantograph.

BRIEF SUMMARY OF THE INVENTION

An object of the invention is to measure several parameters significantof the effective conditions of the overhead line.

Another object of the invention is to make this measurement in anextremely rapid and comfortable manner.

A further object of the invention is to effect this measurementpractically continuously along the entire overhead line.

All these and further objects which will be apparent from the ensuingdescription are attained according to the invention by an apparatus formeasuring the characteristic parameters of an overhead railway ortramway line as described in claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

Some preferred embodiments of the invention are described in detailhereinafter with reference to the accompanying drawings, in which:

FIG. 1 schematically indicates the general principle on which theapparatus of the invention is based,

FIG. 2 shows it in that embodiment for measuring larger variations inthe height of the wire,

FIG. 3 shows it in its general embodiment,

FIG. 4 shows it installed on a railway or tramway vehicle.

DETAILED DESCRIPTION OF THE INVENTION

As can be seen from the figures, the apparatus of the invention isinstalled on board a rail vehicle and is based on the principle of lasertriangulation. For this purpose it comprises a solid state laser sourceable to emit a laser beam 4 which is initially collimated and is thenexpanded to assume a flat form, preferably of the order of 0.2 mm thick.The collimated beam is advantageously expanded by a cylindrical lensformed such as to compensate the gaussian distribution of the laser beamintensity and obtain a uniform intensity.

The laser beam obtained in this manner is projected onto the undersideof the wire 6 of the overhead line at an angle of about 45° to its axis.In this description, reference is always made to a single wire 6,although in practice an overhead line comprises more than one wire.

The interference of the wire 6 with the laser beam 4 determines on thewire a light-emitting line, the pattern and position of which arerelated to the wire profile and hence vary as this varies, in particularas a result of wear, deformation and movement.

In a position below the wire 6 there is located a solid state videocamera 8 of high resolution and high acquisition frequency; its opticalaxis is substantially perpendicular to the axis of the wire 6 and istherefore able to survey the light-emitting line generated by the laserbeam on the wire. The data relative to the line, in the form ofCartesian coordinates of every acquired point thereof, are transferredto a processor unit which calculates the real profile of the lower partof the wire, by interpolating between the plurality of points acquiredby the sensor of the video camera 8.

The processor unit is also able to determine the position of thelight-emitting line which appears in the optical field of the videocamera 8 and to calculate therefrom the horizontal movement of the wirerelative to the axis of the track 10, and its height variations relativeto the plane of the track. More particularly, if for a given height ofthe wire 6 the light-emitting line is located on the optical axis of thevideo camera 8 and its image falls at the centre of the optical fieldthereof, for a slightly different height of the wire 6 thelight-emitting line will be displaced from said optical axis and itsimage will be displaced longitudinally from the centre of said opticalfield to an extent related to the height variations of the wire.

Likewise, if for a central position of the wire 6 the image of thelight-emitting line falls on the median axis of the optical field of thevideo camera 8, for a wire position displaced laterally from thepreceding the image of the light-emitting line on the video camera willbe displaced transversely from said median line to an extent related tosaid displacement.

The video camera 8 is provided with a particular high-selectivityinterferential optical filter, able to allow only the laser wavelengthto pass and to block all other wavelengths, in order to render thesystem immune from interference caused by sunlight or by other lightsourcees and to enable the apparatus to be used in any light condition,without the need for any adjustment.

Using the sampling frequency allowed by the video camera 8 (for example1000/sec), the processor unit is able to measure the threecharacteristic parameters of an overhead railway or tramway linepractically continuously.

The processor unit can be installed on board the railway or tramwayvehicle for immediate measurement of the wire wear, or can be installedon the ground, in which case the data acquired by the video camera 8 arefed to a recorder unit for their later use. In both cases the apparatusof the invention is preferably equipped with a system for measuring theprogressive distance covered, in order to correlate data relative tosuccessive video camera readings with the point on the railway ortramway line at which those data were acquired.

This system preferably consists of an incremental encoder mounted on theaxle of a wheel of the railway or tramway vehicle and connected to thiswheel by an elastic joint or by a toothed belt drive. In order tocompensate possible slippage of the wheels along the rails 10, it ispreferable to use four encoders applied to the four wheels of thevehicle and an algorithm which compares the data originating from saidencoders and corrects the errors due to this slippage.

To make the wire measurement system also reliable in the real case ofseveral large variations in the height of the wire 6 in different or inthe same overhead railway or tramway line, a more sophisticatedapparatus is provided able to adapt automatically to these larger heightvariations, this apparatus being shown schematically in FIG. 2.

As can be seen, in this apparatus the video camera 8 is positioned, forpractical reasons, with its optical axis parallel to the axis of thewire 6, and is faced by a mirror 12 able to reflect onto the videocamera sensor the image of the light-emitting line formed by theinterference of the laser beam 4 with the wire 6.

The video camera 8 is provided with a suitable lens with the possibilityof fixed focus or motorized zoom under the control of the processorunit.

The laser source 2 of this apparatus is coaxial to the video camera 8, amirror 14 being interposed between them to reflect the laser beam 4emitted by said source 2 upwards onto the wire 6.

In operation, starting from a condition, attained by manual or automaticsighting in any manner, in which the image of the light-emitting linefalls within the optical field of the video camera 8, when the systemlogic perceives that as a result of variations in the wire height thisimage of the light-emitting line is about to leave said optical field,it causes the mirror 12 to move in a direction such as to follow thislight-emitting line and return its image to within the field of thevideo camera.

By suitably choosing the system lens perfect focusing and uniformity oflight-emitting characteristics can be ensured, even with a height of thewire 6 variable within a range of 2 m.

In order also to extend the measuring range for the third characteristicparameter of an overhead railway or tramway line, i.e. the horizontalmovement of the wire 6 relative to the track axis, a movement which canreach as much as 0.6 m, the apparatus of the invention uses a pluralityof side-by-side triangulation laser reading units, instead of a singleunit.

FIG. 3 shows an apparatus of this type, in which six laser sources 2 aremounted side by side on a single transverse bar 16 facing a plurality ofmirrors 14 mounted inclined to reflect the laser beam 4.

The six laser sources 2 form part of six reading units, each comprisinga video camera 8, the six video cameras 8 being mounted side by side ona single transverse bar 20 disposed parallel to the bar 16 of the lasersources 2 and facing a bar 22 comprising six mirrors 12 disposed at 45°,to reflect onto the six video cameras 8 the image of the correspondinglight-emitting line formed by the interference of one of the six laserbeams 4 with the wire 6 of the overhead line.

The bar 22 is mounted on a carriage which can be driven by a motorizedscrew for its movement towards and away from said bar 16.

As each reading unit is able to cover a horizontal width of 0.1 m, theassembly of six units is able to cover a total width of 0.6 m, whichnormally corresponds to the maximum horizontal excursion of the wire 6in its movement about the track axis.

The assembly formed by the bar 16 of laser sources 2, the movable mirror14, the bar 20 of video cameras 8 and the bar 22 of fixed mirrors 12 ispreferably enclosed within a strong metal container 24, arranged forfixing to the railway or tramway vehicle 25. Sealed glass windows 26 areprovided in the container 24 to provide visibility for the video cameras8 and an exit for the laser beams 4. These windows are preferablyassociated with electrically driven brushes associated with a series ofdetergent liquid sprayers to provide automatic cleaning. Furthermore, toprevent the formation of condensate on the windows and on the opticalparts of the apparatus, the container 24 is provided with a conditioningsystem able to maintain its internal temperature automatically constant.

As the container 24 is mounted on the railway or tramway vehicle 25 andthe data acquired are influenced by its vertical and horizontalmovements and its rocking, a triangulation laser device 28 is alsoprovided on the bottom of the vehicle to measure the geometricalposition of said vehicle, in order to automatically compensate themeasurement error.

Finally, in addition to the laser triangulation units the apparatus ofthe invention also comprises a further video camera 30 for videoinspection of the overhead line. More particularly, this video camera 30is of progressive scanning digital type with a servo-controlled zoomlens and can be advantageously mounted on the same bar 20 on which thesix video cameras 8 of the six triangulation units are mounted. Likewisea further mirror 32 can be mounted on the same bar 22 as the six mirrors12 to reflect the image of the overhead line onto the video camera 30.

The images acquired by this video camera 30 are compressed in real timeand are then memorized in association with the progressive distancecovered.

From the aforegoing it is apparent that the measuring apparatus of theinvention is particularly advantageous, and in particular:

it enables the three characteristic parameters of an overhead railway ortramway line to be measured, and in particular the wear of the wire, itsheight variations and its displacements about the track axis,

it enables these parameters to be measured practically continuously,

it enables these parameters to be measured very comfortably at highoperating speed,

it enables the measured parameters to be correlated with the progressivedistance covered,

it enables the measurements to be made under any light condition andwithout any influence by sunlight or by other light sources,

the data acquired can be processed in real time, directly on the railvehicle, or subsequently,

it can be integrated with an apparatus for video inspection of theoverhead line,

it automatically compensates the errors due to vertical or horizontalmovements of the railway or tramway vehicle on which it is installed.

What is claimed is:
 1. An apparatus for continuously measuring thecharacteristic parameters of an overhead railway or tramway line,comprising: a laser source for generating a laser beam, optical meansfor transforming said laser beam, generated by said source, into a flatbeam, means for orientating the axis of said flat beam at an angle otherthan 90° to the axis of the overhead line and defining with this lattera plan substantially perpendicular to the plane of said beam, a firstvideo camera having its optical axis different from the axis of saidflat beam but lying in said perpendicular plane and substantiallyorientated upwardly towards the light-emitting line of intersection ofsaid laser beam with said overhead line, and a processing unit for thesignals generated by said first video camera in order to determine theposition of said light-emitting line within the optical field of saidvideo camera, and to effect reconstruction of the real profile of saidoverhead line and its comparison with the theoretical profile of theoverhead line itself.
 2. An apparatus as claimed in claim 1, whereinsaid laser source is a solid state laser source.
 3. An apparatus asclaimed in claim 1, wherein said optical means comprise an assembly oflenses for collimating said laser beam.
 4. An apparatus as claimed inclaim 3, wherein said optical means comprise a cylindrical lens forflattening the collimated beam.
 5. An apparatus as claimed in claim 2,wherein the axis of the flat beam forms with the axis of said wire anangle between 40° and 50°.
 6. An apparatus as claimed in claim 1,wherein said first video camera is of high resolution type.
 7. Anapparatus as claimed in claim 1, wherein said first video camera is ofhigh acquisition frequency type.
 8. An apparatus as claimed in claim 7,wherein said first video camera has sampling frequency of the order of1000 samplings per second.
 9. An apparatus as claimed in claim 1,wherein said first video camera is provided with an interferentialoptical filter of pass band corresponding to the frequency of said lasersource.
 10. An apparatus as claimed in claim 2, wherein said first videocamera is provided with motorized zoom, said first video camera is facedby a mirror movable on the basis of the height of said wire in such amanner as to ensure that the image of said light-emitting line alwaysfalls within the field of said first video camera, said laser source isorientated such that the flat laser beam leaving it is substantiallyparallel to the axis of said wire, and said laser source is faced by amirror projecting the laser beam on the wire, the motorization of thezoom of said first video camera and the movements of said mirror beingcontrolled by said processor unit.
 11. An apparatus as claimed in claim10, characterized in that said first video camera is disposed with itsaxis parallel to the axis of said wire, in a position facing a mirrorwhich reflects onto it the image of said light-emitting line.
 12. Anapparatus as claimed in claim 1 comprising: a plurality of laser sourcesdisposed side by side transverse to the axis of said wire and arrangedto emit a plurality of substantially coplanar flat laser beams, aplurality of first video cameras disposed parallel to said lasersources, the coordinated operation of said first video cameras tomeasure the displacement of said wire about the longitudinal axis of thetrack being controlled by said processor unit.
 13. An apparatus asclaimed in claim 12, comprising a single mirror facing said plurality ofside by side laser sources.
 14. An apparatus as claimed in claim 1,further comprising a second video camera for the video inspection of theoverhead line.
 15. An apparatus as claimed in claim 14, wherein saidsecond video camera for the video inspection of the overhead line ispositioned to the side of said first video camera for determining saidlight-emitting line.
 16. An apparatus as claimed in claim 14, whereinsaid first video camera or said second video camera is disposed with theoptical axis parallel to the wire, facing a mirror arranged to reflectthe image of said wire onto said first or second video camera.
 17. Anapparatus as claimed in claim 1, wherein said laser source and saidfirst video camera are mounted in a container applied to the railway ortramway vehicle and provided with windows for the passage of said laserbeam and of the image of said light-emitting line.
 18. An apparatus asclaimed in claim 17, wherein at least one cleaning brush and at leastone detergent liquid sprayer are associated with each window.
 19. Anapparatus as claimed in claim 17, wherein in addition to said container,there is applied a triangulation device sighted on the rails to measurethe movements of said vehicle relative thereto and to correct saidacquired data on the basis of said movements.